JP5026445B2 - Optical disc apparatus and optical disc recording / reproducing method - Google Patents

Description

  The present invention relates to an optical disc apparatus and an optical disc recording / reproducing method capable of recording / reproducing an optical disc having a multilayered recording layer.

  In recent years, development of optical recording media for recording and reproducing a huge amount of information such as video as digital data has been performed. Examples of such an optical recording medium include CD (Compact Disc), MD (Mini Disc), DVD (Digital Versatile Disc) and the like. Further, in order to further improve the data recording capacity, the recording layer is multilayered.

  Information recorded in each layer of the recording layers thus multilayered is focused on each layer, the recording layer for reading information is detected, and reflected light from the detected recording layer is acquired. Can be read.

  Further, in order to further increase the recording capacity, the recording layer has been further increased in number. Incidentally, a cover layer is provided above the recording layer. In an optical recording medium having a multi-layered recording layer, it is known that spherical aberration occurs due to a difference in the thickness of the cover layer. For this reason, when the laser beam is focused on each layer of the recording layer, it is necessary to correct spherical aberration.

  As a method of setting such a spherical aberration correction value, there is a method of obtaining by automatic adjustment.

  Evaluation value obtained when the recording layer that is in the first focus-on state for a given recording layer is changed to a different value on the basis of the preset spherical aberration correction value as a reference. To get. Based on the result, a spherical aberration correction value is determined.

  Further, Patent Document 1 discloses using a spherical aberration correction value adjusted to an intermediate point between the target layer and the second recording layer, or a spherical aberration correction value shifted by a predetermined value.

  This will be described with reference to FIG.

  FIG. 10 is an explanatory diagram when the spherical aberration correction method is performed by the technique of Patent Document 1. In FIG.

  Among the plurality of recording layers, the second recording layer (L1 layer) and the first recording layer (L0 layer) are formed from the laser beam incident side, and the target layer is the L0 layer.

  When focusing on the L0 position, a focus-on spherical surface to the L0 layer is obtained by shifting a value obtained by shifting to the midpoint between the L0 layer and the L1 layer based on the shift value obtained by the automatic adjustment from the midpoint. It is set as an aberration correction value (position of arrow Q in FIG. 10).

  As a result, L0 can be detected.

  Further, in Patent Document 2, the spherical aberration correction amount is adjusted so that the SUM signal becomes the correction amount at the minimum value before the start of focus servo. After the start of the focus servo, the spherical aberration correction amount is adjusted so as to be a correction amount at a maximum value corresponding to the recording layer on which the laser beam is focused, out of the two maximum values. Focus servo control can be performed at a position where the S curves of both recording layers are not easily distorted.

JP 2008-123666 A (published May 29, 2008) JP 2008-186505 A (released on August 14, 2008)

  Here, in the optical disk having a multi-layered recording layer, the reflectance of each recording layer is relatively lowered, and therefore the reflectance of the cover layer is relatively increased. There may be a case where the reflectance of the cover layer is equivalent to that of each recording layer.

  This is shown in FIG.

  FIG. 11 is an explanatory diagram illustrating a state in the case where the reflectance of the cover layer is relatively large, which is the conventional technique disclosed in Patent Document 2.

  As shown in FIG. 11, the reflectivity of the cover layer is relatively large, and the signal level at the position L10 representing the position of the cover layer is at the position of each of L2, L1, and L0 representing the position of each recording layer. It is equivalent to the signal level.

  Some optical disc apparatuses are designed not to count the cover layer as the number of layers. In the case of such an optical disk device, for example, in the case of an optical disk having two recording layers, the design is based on the premise that only L0 and L1 are counted. If the reflectance from the cover layer is small, there is no problem, but if the reflection from the cover layer is large, the cover layer will be counted, and the desired recording layer cannot be detected, and the predetermined layer Focus servo control cannot be performed.

  Manufacturer information, media information, and the like are recorded on the recording layer (that is, L0) arranged at the farthest position from the laser light irradiation surface, and L0 needs to be reliably recognized.

  In the prior art shown in FIG. 10, only two layers for which the cover layer is counted are counted. The second layer is recognized as L0.

  In the prior art shown in FIG. 11, the cover layer is also counted and the third layer is recognized as L1. For this reason, if the design is such that the cover layer is not counted (that is, the design is such that only three recording layers are counted for a three-layer disc), L0 cannot be recognized. That is, the third layer is not recognized as L0. In an optical disc having a relatively high reflectivity of the cover layer, the cover layer is counted due to the influence of surface blurring on the signal from the cover layer, and as a result, there is a problem that the focus cannot be pulled into L0.

  An object of the present invention is to provide an optical disc apparatus and an optical disc recording / reproducing method capable of preventing erroneous detection of a recording layer and improving work efficiency.

  In order to solve the above-described problems, an optical disc apparatus according to the present invention causes a laser beam to be incident on an optical recording medium in which a protective layer and a plurality of recording layers are arranged, and the laser from the plurality of recording layers. An optical disc apparatus that detects a recording layer that records or reproduces information among the plurality of recording layers based on the intensity of reflected light of the light. Spherical aberration correcting means for correcting the spherical aberration with respect to a reference recording layer, which is a recording layer disposed farthest from the protective layer, among the plurality of recording layers. The spherical aberration correction value is corrected from the position where the reference recording layer is disposed to the position opposite to the position where the protective layer is disposed.

  In the optical disk recording / reproducing method of the present invention, laser light is incident on an optical recording medium provided with a protective layer and a plurality of recording layers, and the reflected light of the laser light from the plurality of recording layers is reflected. An optical disc recording / reproducing method for detecting a recording layer for recording or reproducing information among the plurality of recording layers based on intensity, wherein spherical aberration generated in the laser light is determined based on intensity of the reflected light. A spherical aberration correction step for correcting, and in the spherical aberration correction step, spherical aberration with respect to a reference recording layer, which is a recording layer disposed farthest from the protective layer among the plurality of recording layers, is converted into the reference recording layer. Is corrected with a spherical aberration correction value adjusted to a position opposite to the position where the protective layer is disposed.

  Here, it is known that spherical aberration occurs in the laser light incident on an optical recording medium in which a protective layer and a plurality of recording layers are laminated. For this reason, in order to accurately detect the recording layer to be detected among the plurality of recording layers, it is necessary to correct the spherical aberration of the laser beam in which the spherical aberration has occurred.

  Further, the spherical aberration correcting means includes the reference recording layer when correcting the spherical aberration with respect to the reference recording layer, which is the recording layer arranged farthest from the protective layer among the plurality of recording layers. From the position, correction is performed with a spherical aberration correction value adjusted to a position opposite to the position where the protective layer is disposed.

  Thereby, compared with the intensity of the reflected light from the reference recording layer, the intensity of the reflected light from the recording layer disposed adjacent to the reference recording layer among the plurality of recording layers can be suppressed. .

  For this reason, when detecting the reference recording layer, it is possible to prevent erroneous detection of the recording layer adjacent to the reference recording layer. Thus, since it is possible to detect the reference recording layer with high accuracy, it is not necessary to change the threshold value for detecting the intensity of reflected light from the reference recording layer in order to detect the reference recording layer. Work efficiency can be improved.

  As described above, according to the above configuration, it is possible to configure an optical disc apparatus that can prevent erroneous detection of the recording layer and improve work efficiency.

  The optical disc apparatus further includes spherical aberration correction value calculation means for calculating the spherical aberration correction value from the intensity of the reflected light, and the spherical aberration correction means includes the spherical aberration calculated by the spherical aberration correction value calculation means. It is preferable to correct the spherical aberration based on the correction value.

  With the above configuration, since the spherical aberration correction value calculation means calculates the spherical aberration correction value based on the intensity of the reflected light, the spherical aberration correction value for detecting the reference recording layer can be calculated more accurately. can do. The spherical aberration correction unit corrects the spherical aberration based on the spherical aberration correction value calculated by the spherical aberration correction value calculation unit, so that the reference recording layer can be detected more accurately. An optical disc device that can be used can be configured.

  The optical disc apparatus preferably further includes laser light intensity control means for controlling the intensity of the laser light.

  According to the above configuration, the intensity of the reflected light can be controlled by the laser light intensity control means controlling the intensity of the laser light. That is, since the intensity of the reflected light from the reference recording layer can be controlled, the intensity of the reflected light from the reference recording layer is arranged adjacent to the reference recording layer among the plurality of recording layers. The difference from the intensity of the reflected light from the recording layer can be finely adjusted. Thereby, the prevention effect of the erroneous detection at the time of detecting the reference recording layer can be improved. Further, it is possible to further reduce the necessity of changing the threshold value for detecting the intensity of the reflected light from the reference recording layer in order to detect the reference recording layer.

  The optical disc apparatus of the present invention makes laser light incident on an optical recording medium in which a protective layer and a plurality of recording layers are arranged, and based on the intensity of reflected light of the laser light from the plurality of recording layers. An optical disc apparatus for detecting a recording layer for recording or reproducing information among the plurality of recording layers, wherein spherical aberration correcting means corrects spherical aberration generated in the laser light based on the intensity of the reflected light. The spherical aberration correcting means includes a spherical aberration with respect to a reference recording layer, which is a recording layer arranged farthest from the protective layer among the plurality of recording layers, from a position where the reference recording layer is provided. The correction is made with the spherical aberration correction value adjusted to the position opposite to the position where the protective layer is disposed.

  In the optical disk recording / reproducing method of the present invention, laser light is incident on an optical recording medium in which a protective layer and a plurality of recording layers are arranged, and the intensity of reflected light of the laser light from the plurality of recording layers is increased. An optical disc recording / reproducing method for detecting a recording layer for recording or reproducing information among the plurality of recording layers, wherein spherical aberration generated in the laser light is corrected based on the intensity of the reflected light. A spherical aberration correction step, wherein in the spherical aberration correction step, the reference recording layer arranges spherical aberration with respect to a reference recording layer which is the recording layer farthest from the protective layer among the plurality of recording layers. From this position, correction is performed with a spherical aberration correction value adjusted to a position opposite to the position where the protective layer is disposed.

  Thereby, it is possible to prevent erroneous detection of the recording layer and to improve the working efficiency.

FIG. 1 is a block diagram showing a schematic configuration of an optical disc apparatus according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing the movement of the focus position of the laser beam in the optical disc apparatus of FIG. FIG. 3 is a schematic diagram showing reflected light from the optical disk as FES and SUM signals. FIG. 4 is a first flowchart showing an operation flow of the optical disc apparatus of FIG. FIG. 5 is a second flowchart showing the flow of operations of the optical disc apparatus of FIG. FIG. 6 is a diagram showing the relationship between the spherical aberration correction amount and the peak value of the SUM signal of each layer. FIG. 7 is a schematic diagram showing reflected light from a three-layer disc as FES and SUM signals. FIG. 8 is a diagram showing the relationship between the spherical aberration correction amount and the peak value of the SUM signal of each layer in the three-layer disc. FIG. 9 is a flowchart showing an operation flow of the optical disk apparatus of FIG. 1 in a three-layer disk. FIG. 10 is an explanatory view for explaining a spherical aberration correction method of a conventional optical disc apparatus. FIG. 11 is an explanatory view for explaining a spherical aberration correction method of a conventional optical disc apparatus.

  Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 1 is a block diagram showing a schematic configuration of an optical disc apparatus 1 according to the present embodiment.

  As shown in FIG. 1, the optical disc apparatus 1 of the present invention includes a cover layer 63 (protective layer), a first recording layer 60 (recording layer, reference recording layer), and a second recording layer 62 (recording layer) as a plurality of recording layers. The laser beam 25 is made incident on the optical disc 65 (optical recording medium) on which the layer is disposed. Based on the intensity of the reflected light of the laser beam 25 from the first recording layer 60 and the second recording layer 62, a recording layer that records or reproduces information among the first recording layer 60 and the second recording layer 62. (Target layer) is detected.

  The optical disc apparatus 1 also includes a collimator lens 22 (spherical aberration correcting unit) that corrects spherical aberration generated in the laser beam 25 based on the intensity of the reflected light, and a spherical aberration correcting unit 12 (spherical aberration correcting unit). .

  The collimator lens 22 and the spherical aberration correction unit 12 are spherical aberration with respect to the first recording layer 60 that is the recording layer farthest from the cover layer 63 among the first recording layer 60 and the second recording layer 62. Is corrected with a spherical aberration correction value adjusted from the position where the first recording layer 60 is disposed to the position opposite to the position where the cover layer 63 is disposed.

  In the optical disc 65, a first recording layer 60 and a second recording layer 62 are laminated on a substrate 64, and an intermediate layer 61 is disposed between the first recording layer 60 and the second recording layer 62. Yes. A cover layer 63 is disposed above the second recording layer 62.

  That is, in the optical disc 65, the cover layer 63 becomes the incident surface of the laser beam 25, and the cover layer 63, the second recording layer 62, the intermediate layer 61, the first recording layer 60, and the substrate 64 are sequentially formed from the incident direction of the laser beam 25. Is arranged.

  The optical disk 65 may be a reproduction-only recording medium, a write-once recording medium, or a rewritable recording medium. For example, a CD (Compact Disc), an MD (Mini Disc), a DVD (Digital Versatile Disc), or a BD (Blu) -ray Disc: registered trademark). Further, the plurality of recording layers arranged on the optical disc used in the optical disc apparatus 1 is not limited to two layers, and may have a structure in which three or more recording layers are laminated. The case where the optical disc 66 (optical recording medium), which is an optical disc in which three recording layers are arranged, is used in the optical disc apparatus 1 to be described later.

  As shown in FIG. 1, the incident surface of the cover layer 63 where the laser beam 25 is incident is L10, the interface between the second recording layer 62 and the cover layer 63 is L1, and the first recording layer 60 and the intermediate layer are arranged. The interface of 61 is set as the position of L0.

  The optical head 20 adjusts the focus of the laser light source 21 that is a light source of the laser light 25, a collimator lens 22 for correcting spherical aberration generated in the laser light 25, and the laser light 25 that passes through the collimator lens 22. And an objective lens 23 for receiving the reflected light reflected from the optical disk 65. Furthermore, a beam splitter 26 that reflects the reflected light from the optical disc 65 and makes it incident on the detector 27, and a detector 27 that converts the reflected light emitted from the beam splitter 26 into an electrical signal corresponding to the intensity thereof.

  The laser light source 21 is a light source for generating laser light 25, and is made of, for example, a semiconductor laser. In the following description, the irradiation direction of the laser beam 25 or the opposite direction may be referred to as an optical axis direction (direction of arrow Y in FIG. 1), and the central axis of the laser beam 25 may be referred to as an optical axis.

  Further, the irradiation direction of the laser beam 25 is referred to as an optical axis + direction, and the irradiation direction and the reflection direction of the laser beam 25 are referred to as an optical axis-direction.

  The detector 27 only needs to be capable of changing light into a current, and is made of, for example, a photodiode.

  In the optical head 20, a laser light source 21, a beam splitter 26, a collimator lens 22, and an objective lens 23 are disposed on the optical axis, and the laser light 25 emitted from the laser light source 21 is transmitted in this order and the optical disk 65 is disposed. Is irradiated. Reflected light from the optical disk 65 passes through the objective lens 23 and the collimator lens 22, is reflected by the beam splitter 26, and enters the detector 27. Then, it is converted into an electric signal by the detector 27.

  The optical head control unit 10 controls the driving of the optical head 20 and adjusts the focus servo control unit 11 for adjusting the focal position (focus) of the objective lens and the position of the collimator lens 22 on the optical axis. Thus, the spherical aberration correction unit 12 that corrects the spherical aberration and the reproduction power control unit 13 that controls the intensity of the laser beam 25 emitted from the laser light source 21 are provided. The collimator lens 22 corrects the spherical aberration of the laser light 25, and a liquid crystal element can be used instead of the collimator lens 22. In this case, it is necessary to provide a drive circuit that performs drive control of the liquid crystal element.

  The data conversion unit 30 acquires an electrical signal obtained by photoelectrically converting the reflected light by the detector 27. The electrical signal is converted into an analysis control signal.

  Examples of the analysis control signal include FES (focus error signal), SUM signal, and RF signal. For these FES, SUM signal, RF signal, and the like, a generally used method can be used in this embodiment mode, and thus detailed description is omitted. In the present embodiment, description will be given using the FES and SUM signals.

  In addition, the data conversion unit 30 includes a target layer detection unit 31. The target layer detection unit 31 detects the target layer and determines whether or not the target layer has been successfully focused.

  The spherical aberration correction value calculation unit 40 calculates a spherical aberration correction value for correcting the spherical aberration generated in the laser light 25 from the intensity of the reflected light. When the spherical aberration correction value calculation unit 40 acquires the analysis signal output from the data conversion unit 30, the spherical aberration correction value calculation unit 40 calculates a spherical aberration correction value based on the acquired analysis signal. Then, the spherical aberration correction value calculator 40 causes the spherical aberration corrector 12 to correct the spherical aberration of the laser beam 25 by outputting the calculated spherical aberration correction value to the optical head controller 10.

  The optical disc apparatus 1 includes a system control unit (not shown) that performs system control of the entire optical disc apparatus 1, an input device that receives input from a user, a display device that displays signals and information to the user, and the like. Prepare.

  Next, the focusing operation of the optical disc apparatus 1 will be described with reference to FIG.

  FIG. 2 is a schematic diagram showing how the focus position of the laser beam 25 moves.

  The optical disc apparatus 1 controls the focus position of the laser beam 25 in order to reproduce information recorded on each recording layer of the optical disc 65 or record information on each recording layer. This is because the focus servo control unit 11 controls the focus servo of the objective lens 23 to move the focus position of the laser light by moving the position of the objective lens 23 in the optical axis direction.

  In FIG. 2, the focus servo control unit 11 moves the objective lens 23 in the optical axis direction so that the laser beam 25 is focused on the position L10 (the state of the laser beam 25 on the left side in FIG. 2), L1. The state in which the laser beam 25 is focused on the position (the state of the middle laser beam 25 in FIG. 2), the state in which the laser beam 25 is focused on the position L0 (the state of the laser beam 25 on the right side in FIG. 2). Represents.

  Here, since the layers stacked on the optical disc 65 have different reflectances, when the focus position of the laser beam 25 is moved, the intensity of the reflected light changes at the interface between the layers. This change is expressed as an S-shaped signal by FES, for example, as shown in FIG. In addition, the signal level is amplified in the SUM signal. For example, at the position of L10, the position of L2, the position of L1, and the position of L0, FES generates an S-shaped signal, and the signal level of the SUM signal has an amplitude.

  Next, the method for correcting the spherical aberration from the S-signal with the amplitude of the signal level of the SUM signal and the FES as described above will be described with reference to FIGS. The target layer is the first recording layer 60.

  FIG. 3 is a schematic diagram showing the reflected light from the optical disk 65 of the laser light 25 as FES and SUM signals.

  The data converter 30 converts the electrical signal output from the detector 27, which is an electrical signal based on the intensity of the reflected light, into an FES or SUM signal as an analysis signal.

  Here, as shown in FIG. 3, the threshold of the SUM signal for the target layer detection unit 31 to detect the first recording layer 60 that is the target layer (in other words, to detect the position of L0) is VSUM_TH, and FES The threshold value is VFES_TH. The cover layer 63 has a relatively high reflectance and often exceeds the threshold value.

  Then, the spherical aberration correction unit 12 moves the position of the collimator lens 22 in the optical axis direction so that the spherical aberration with respect to L0 of the laser light 25 is changed from the position of L0 to the optical axis + direction (the substrate 64 is disposed). Correction is performed with a spherical aberration correction value adjusted to a position separated by Δx in the direction).

  Accordingly, the peak value of the SUM signal at the position of L1 (or the peak value of the S-shaped signal of FES) is compared with the peak value of the SUM signal at the position of L0 (or the peak value of the S-shaped signal of FES). Can be suppressed.

  Therefore, when the first recording layer 60 is detected, it is possible to prevent the recording layer adjacent to the reference recording layer from being erroneously detected even if the threshold value VSUM_TH (or the threshold value VFES_TH) is constant. That is, it is possible to suppress the peak value of the SUM signal at the position of L1 from exceeding the threshold value VSUM_TH (or the peak value of the F-shaped S-shaped signal from exceeding the threshold value VFES_TH).

  Thus, since the position of L0 can be detected with high accuracy, it is not necessary to change the threshold value VSUM_TH (or the threshold value VFES_TH) in order for the target layer detection unit 31 to detect the first recording layer 60. It becomes possible to improve the work efficiency for detecting the position of L0. Thereby, it is possible to prevent the erroneous detection of the target layer of the target layer detection unit 31 and to configure the optical disc apparatus 1 with improved work efficiency.

  Then, the optical disc apparatus 1 can irradiate the first recording layer 60 with the laser light 25 whose spherical aberration has been corrected by the spherical aberration correction value, and perform focus pull-in to the first recording layer 60.

  On the other hand, when the target layer is the first recording layer 60, when the spherical aberration correction of the laser beam 25 is performed in the optical axis minus direction (the direction in which the cover layer 63 is disposed) from the position of L0, a position other than L0. The peak value of the SUM signal detected at (or the peak value of the F-shaped S-shaped signal) increases, and the difference from the amplitude of the SUM signal detected at the position L0 decreases. For this reason, it is highly possible that the peak value of the SUM signal (or the peak value of the S-shaped signal of the FES) exceeds the threshold value VSUM_TH (or the threshold value VFES_TH) at a position other than L0, and may be erroneously detected by the target layer detection unit 31. Increases nature.

  Further, by adjusting the reproduction power (intensity of the laser beam 25) by the reproduction power control unit 13, the signal level can be adjusted as a whole, and the peak value (or the SUM signal at the position of L0 (or The difference between the peak value of the FES S-shaped signal) and the peak value of the SUM signal at a position other than L0 (or the peak value of the FES S-shaped signal) can be finely adjusted. In this fine adjustment, the reproduction power is adjusted to the extent that there is no influence on each recording layer. In other words, the reproduction power is finely adjusted so that the reproduction power does not become so high that the state of each recording layer changes. Thereby, the prevention effect of the false detection at the time of the target layer detection part 31 detecting L0 can be improved. In addition, it is possible to further reduce the need to change the threshold value VSUM_TH (or the threshold value VFES_TH) in order to detect L0. For this reason, the focus pull-in of the first recording layer 60 can be performed more stably.

[Spherical aberration correction value BE]
Next, the spherical aberration correction value calculated by the spherical aberration correction value calculation unit 40 will be described.

  In the present embodiment, when the spherical aberration correction value is BE, BE is expressed by the following equation.

Spherical aberration correction value BE = BE0 + α (1)
(BE0: spherical aberration correction value corresponding to L0, α> 0)
Further, when BE1 is a spherical aberration correction value corresponding to L1, the following equation is established. 0 <BE1 <BE0 (2)
That is, when detecting L0, the spherical aberration correction value calculation unit 40 calculates the spherical aberration correction value by adding α to the spherical aberration correction value corresponding to L0.

[Method of determining α]
Next, a method for setting α will be described.

  Note that α may be set as appropriate, but can be set reliably by using the following relational expression.

  Here, an example in the case of using a SUM signal will be described.

  When the optical disc 65 is reproduced with a certain reproduction power, the following relationship is generally established.

V = R (−a | x | + b) (3)
V: Peak value of SUM signal in a certain layer (only V> 0)
R: reflectivity of a layer a, b: constant determined by reproduction power (uniquely determined by optical disk device)
| X |: Absolute value of the difference between the distance from the surface of the cover layer 63 to a certain layer and the distance from the surface of the cover layer 63 corresponding to the set spherical aberration correction amount Here, a and b are used It is a constant uniquely determined by the optical disk playback device and needs to be known in advance. When a BD evaluation machine (ODU-1000) manufactured by Pulstec Corporation is used as the optical disc apparatus 1, when the reproduction power is 0.7 mW, a = 10 and b = 43.

  In addition, it is necessary to grasp the reflectivity R by checking the signal level of the SUM signal of each recording layer in advance on the optical disk to which the focus is drawn. The reflectance R is derived by confirming the spherical aberration correction value for a known layer thickness (for example, 100 μm for L0 and 75 μm for L1 of a two-layer disc in which two general recording layers are laminated). It is also possible.

  When spherical aberration correction is performed at a position away from L0 by Δx in the optical axis + direction from L0 (the direction opposite to the position of L10), the focus can be pulled into L0 as follows. The relationship between VSUM_TH, V1, and V0 shown is when V1 is smaller than VSUM_TH and V0 is larger than VSUM_TH.

VSUM_TH: SUM signal threshold value for focusing on a certain layer V0: SUM signal peak value at position L0 V1: Peak value of SUM signal at position L1 That is, the following relational expression is satisfied. .

V1 <TSUM_TH <V0 (4)
Thus, from the relationship with the above-described equation (3), by setting α corresponding to Δx when the following equation holds, the spherical aberration compensation value that is estimated to be capable of drawing the focus to L0 is set. Can do.

V1 = R1 (−a | Δx + x0−x1 | + b) <VSUM_TH (5)
V0 = R0 (−a | Δx | + b)> VSUM_TH (6)
Here, it is not uniquely determined as Δx, and a value in a certain range satisfies the above expressions (5) and (6). Therefore, if the lower limit value of Δx that satisfies the equations (5) and (6) is xmin and the upper limit value is xmax, Δx is expressed as follows.

xmin <Δx <xmax (7)
When the value of α corresponding to this is αmin <α <αmax, the value of α can be set as follows, for example.

α = (αmin + αmax) / 2 (8)
Here, α satisfying the above equation (8) will be described with reference to FIG. FIG. 6 shows the relationship between the spherical aberration correction amount and the peak value of the SUM signal of each layer. Here, a method for determining α in the case of a dual-layer disc will be described.

  For example, when spherical aberration correction corresponding to L0 is performed, the peak value of the L0 SUM signal is maximum. Further, when the spherical aberration correction corresponding to L1 is performed, the peak value of the SUM signal of L1 is the maximum. The spherical aberration correction corresponding to α satisfying the above equation (8), that is, the position of the arrow A in FIG. 6 is performed.

  In this way, the optical disc 65 is rotated by performing spherical aberration correction so that VSUM_TH is in the vicinity of the middle between the peak value V1 of the L1 SUM signal and the peak value V1 of the L0 SUM signal. The SUM signal at the position of L0 can be separated by the threshold value VSUM_TH once set without being affected by the surface blurring due to. For this reason, in order for the target layer detection part 31 to detect each recording layer, it is not necessary to change a threshold value.

[Flowchart 1]
Next, the operation flow of the optical disc apparatus 1 will be described with reference to FIG.

  FIG. 4 is a flowchart showing an operation flow of the optical disc apparatus 1.

  First, in step S101, the optical disc 65 is loaded into the optical disc apparatus 1. Then, when the optical disk device 1 detects that the optical disk 65 is loaded, the optical disk device 1 rotates the optical disk 65 at a predetermined linear velocity. Then, according to an instruction from the optical head control unit 10, the optical head 20 moves to a predetermined radial position of the optical disk 65.

  Next, in S <b> 102, the optical head control unit 10 outputs a laser light output instruction for outputting the laser light 25 with a predetermined reproduction power to the laser light source 21. When the laser light source 21 receives the laser light output instruction from the optical head controller 10, the laser light source 21 irradiates the optical disk 65 with the laser light 25 with a predetermined reproduction power.

  The optical head 20 receives the reflected light from the optical disk 65. The reflected light received by the optical head 20 passes through the objective lens 23 and the collimator lens 22, is reflected by the beam splitter 26, and enters the detector 27. Thereby, the reflected light from the optical disk 65 is converted into an electric signal. The detector 27 then outputs the converted electrical signal to the data converter 30.

  When the data converter 30 acquires an electrical signal from the detector 27, the data converter 30 converts the acquired electrical signal into an FES, a SUM signal, or the like. Then, the data conversion unit 30 outputs the converted FES, SUM signal, and the like to the spherical aberration correction value calculation unit 40. The data conversion unit 30 may output only one of the FES and SUM signals to the spherical aberration correction value calculation unit 40, or may output both.

  Next, in S103, when the spherical aberration correction value calculation unit 40 acquires one or both of the FES and SUM signals from the data conversion unit 30, it sets the spherical aberration correction value BE from the acquired FES and SUM signals. To do. Here, assuming that the target layer is L0, the spherical aberration correction value BE set by the spherical aberration correction value calculator 40 is BE = BE0 + α. Then, the spherical aberration correction value calculation unit 40 outputs the set spherical aberration correction value BE to the optical head control unit 10.

  Then, when the optical head control unit 10 acquires the spherical aberration correction value BE from the spherical aberration correction value calculation unit 40, the spherical aberration correction unit 12 performs the optical axis direction of the collimator lens 22 based on the spherical aberration correction value BE. Is adjusted to correct the spherical aberration of the laser beam 25. Thereby, the target layer detection part 31 detects a target layer.

  In step S <b> 104, the optical head control unit 10 outputs a focus pull-in instruction for starting focus pull-in of the target layer to the optical head 20. Here, the optical head control unit 10 outputs a focus pull-in instruction for performing the focus pull-in to L0 to the optical head 20. When the optical head 20 acquires the focus pull-in instruction output from the optical head controller 10, the optical head 20 starts focus pull-in to L0.

  In S105, the data conversion unit 30 acquires the electrical signal output from the detector 27 after the focus pull-in is started, and converts it into the FES and SUM signals. Then, the target layer detection unit 31 determines whether or not the focus pull-in is successful from the FES or SUM signal converted by the data conversion unit 30.

  When the target layer detection unit 31 determines that the focus pull-in is successful (YES in S105), the spherical aberration correction is terminated. When the target layer detection unit 31 determines that the focus pull-in has failed (NO in S105), the data conversion unit 30 outputs the FES and SUM signals to the spherical aberration correction value calculation unit 40.

  Next, in S106, the spherical aberration correction value calculation unit 40 changes the spherical aberration correction value BE again by changing the value of α. Then, the spherical aberration correction value calculation unit 40 outputs the changed spherical aberration correction value BE to the optical head control unit 10. Then, the spherical aberration correction unit 12 adjusts the position of the collimator lens 22 in the optical axis direction by the spherical aberration correction value BE acquired from the spherical aberration correction value calculation unit 40, and performs spherical aberration correction. Then, the process returns to S104.

[Flowchart 2]
Next, a processing flow of the optical disc apparatus 1 when the reproduction power of the laser beam 25 is changed together with the spherical aberration correction will be described with reference to FIG.

  FIG. 5 is a flowchart showing the processing flow of the optical disc apparatus 1 when the reproduction power of the laser beam is also changed.

  In the process of S105 of FIG. 4, when the target layer detection unit 31 determines that the focus pull-in has failed (NO in S105), the target layer detection unit 31 outputs the determination result to the reproduction power control unit 13.

  In step S <b> 201, when the reproduction power control unit 13 obtains a determination result from the target layer detection unit 31, the reproduction power control unit 13 determines whether the reproduction power can be changed.

  Here, the reproduction power control unit 13 can change the reproduction power by checking whether or not all the reproduction power conditions set in advance have been tried or whether or not the reproduction power should be changed in advance. Determine whether. These settings are assumed to be preset by a user or the like in a storage unit (not shown) provided inside or outside the reproduction power control unit 13.

  The setting range of the preset reproduction power condition to be stored in the storage unit is, for example, within ± 10% of the reproduction power recommended by DI (Disc Information), etc. The range of reproduction power can be mentioned. The DI of the optical disk that has been used once is stored in the storage unit as reference information. In addition, for example, it is preferable to store information such as information that is effective when the playback power is higher than DI in some commercially available RE_DL discs as reference information. As a result, when reproducing an optical disk having the same DI, the reproduction power control unit 13 can set the reproduction power more quickly and accurately by reading the reference information from the storage unit. However, when the reproduction power is increased, it may be assumed that there is damage to the optical disk, so it is desirable to set from a low reproduction power.

  Next, when the reproduction power control unit 13 determines that the reproduction power cannot be changed (NO in S201), the reproduction power control unit 13 ends the change of the reproduction power and proceeds to S106.

  If the reproduction power control unit 13 determines that the reproduction power can be changed (YES in S201), the reproduction power is changed in S202. Thereby, the laser light source 21 changes the intensity and irradiates the laser light 25.

  In step S <b> 203, the optical head control unit 10 outputs to the optical head 20 a focus pull-in instruction for performing focus pull-in to the target layer L <b> 0. When the optical head 20 acquires the focus pull-in instruction output from the optical head controller 10, the optical head 20 starts focus pull-in to L0.

  Next, in S204, the data conversion unit 30 acquires an electrical signal output from the detector 27 after the focus pull-in is started, and converts it into an FES and SUM signal. Then, the target layer detection unit 31 determines whether or not the focus pull-in is successful from the FES or SUM signal converted by the data conversion unit 30.

  When the target layer detection unit 31 determines that the focus pull-in is successful (YES in S204), the spherical aberration correction is terminated. When the target layer detection unit 31 determines that the focus pull-in has failed (NO in S204), the target layer detection unit 31 outputs the determination result to the reproduction power control unit 13. Then, the process returns to S201.

  In the present embodiment, a BD evaluation machine (ODU-1000) manufactured by Pulstec Corporation is used as the optical disc apparatus 1.

  As described above, according to the optical disc apparatus 1, the signal level of the SUM (RF signal), the FES, etc. is adjusted without changing the threshold for detecting the SUM signal (RF signal), the FES, etc. Allows focus to be pulled into the layer.

  Spherical aberration correction of the laser beam 25 is performed with a spherical aberration correction value corresponding to a position farther from L0 (L10, L1 SUM signal and FES signal levels are made lower than L0 SUM signal and FES signal levels). ). Further, the reproduction power is changed to uniformly change the L10, L1, and L0 SUM signals and the FES. Thereby, it is possible to reliably perform the focus pull-in to L0.

[For discs with 3 or more recording layers]
Next, the case where an optical disc having three or more recording layers is used in the optical disc apparatus 1 will be described. The optical disc apparatus 1 may use an optical disc having three or more recording layers instead of the optical disc 65 having two recording layers (the first recording layer 60 and the second recording layer 62). Here, a case of a three-layer disc (an optical disc having three recording layers) will be described with reference to FIGS. 1 and 7 to 9.

  The optical disc 66 (optical recording medium), which is a three-layer disc, has a second intermediate layer and a third recording layer (L2 layer) laminated between the second recording layer 62 and the cover layer 63 of the optical disc 65. It is the structure which was made. Then, the position of the interface between the third recording layer and the cover layer 63 is set as the position L2.

  FIG. 7 is a schematic diagram showing the reflected light from the optical disc 66 of the laser beam 25 in the three-layer disc as FES and SUM signals. FIG. 8 is a diagram showing the relationship between the spherical aberration correction amount in the three-layer disc and the peak value of the SUM signal of each layer.

  When spherical aberration correction is performed in the optical axis + direction from L0 (the direction opposite to the position of L10) at a position away from L0 by Δx (the position of arrow B), it is possible to pull the focus into L0. This is the case when the following relationship between VSUM_TH, V2, V1, and V0 is such that V1 or V2 is smaller than VSUM_TH and V0 is larger than VSUM_TH.

VSUM_TH: SUM signal threshold value for performing focus pull-in to a certain layer V2: SUM signal peak value at position L2 V1: SUM signal peak value at position L1 V0: SUM signal peak at position L0 In this way, by setting α corresponding to Δx when the following expression satisfies the above relationship, it is possible to set a spherical aberration compensation value that is estimated to allow focus pull-in to L0.

V2 = R2 ′ (− a | Δx + x0−x2 | + b) (9)
V1 = R1 ′ (− a | Δx + x0−x1 | + b) (10)
V0 = R0 ′ (− a | Δx | + b) (11)
For example, in the case of FIG. 8, by performing spherical aberration correction corresponding to the position of the arrow C, the SUM signal at the position L0 is once transmitted without being affected by surface blurring caused by the rotation of the optical disk 66. Separation is possible with VSUM_TH which is a set threshold value. For this reason, in order for the target layer detection part 31 to detect each recording layer, it is not necessary to change a threshold value.

  Next, the flow of operation of the optical disc apparatus 1 when performing focus pull-in on the optical disc 66 will be described with reference to FIG.

  FIG. 9 is a flowchart showing the operation flow of the optical disc apparatus 1.

  First, in step S301, the optical disk 66 is loaded into the optical disk apparatus 1. When the optical disc apparatus 1 detects that the optical disc 66 is loaded, the optical disc device 1 rotates the optical disc 66 at a predetermined linear velocity. Then, according to an instruction from the optical head control unit 10, the optical head 20 moves to a predetermined radial position on the optical disk 66.

  In step S <b> 302, the optical head control unit 10 outputs a laser beam output instruction for outputting the laser beam 25 with a predetermined reproduction power to the laser light source 21. Then, when the laser light source 21 obtains a laser light output instruction from the optical head controller 10, the laser light source 21 irradiates the optical disk 66 with the laser light 25 with a predetermined reproduction power.

  The optical head 20 receives the reflected light from the optical disk 66. The reflected light received by the optical head 20 passes through the objective lens 23 and the collimator lens 22, is reflected by the beam splitter 26, and enters the detector 27. Thereby, the reflected light from the optical disk 66 is converted into an electric signal. The detector 27 then outputs the converted electrical signal to the data converter 30.

  When the data converter 30 acquires an electrical signal from the detector 27, the data converter 30 converts the acquired electrical signal into an FES, a SUM signal, or the like. Then, the data conversion unit 30 outputs the converted FES, SUM signal, and the like to the spherical aberration correction value calculation unit 40. The data conversion unit 30 may output only one of the FES and SUM signals to the spherical aberration correction value calculation unit 40, or may output both.

  In step S303, when the spherical aberration correction value calculation unit 40 acquires one or both of the FES and SUM signals from the data conversion unit 30, the spherical aberration correction value calculation unit 40 sets the spherical aberration correction value BE from the acquired FES and SUM signals. To do. Here, assuming that the target layer is L0, the spherical aberration correction value BE set by the spherical aberration correction value calculator 40 is BE = BE0 + α. Then, the spherical aberration correction value calculation unit 40 outputs the set spherical aberration correction value BE to the optical head control unit 10.

  Then, when the optical head control unit 10 acquires the spherical aberration correction value BE from the spherical aberration correction value calculation unit 40, the spherical aberration correction unit 12 performs the optical axis direction of the collimator lens 22 based on the spherical aberration correction value BE. Is adjusted to correct the spherical aberration of the laser beam 25. Thereby, the target layer detection part 31 detects a target layer.

  In step S <b> 304, the optical head control unit 10 outputs a focus pull-in instruction for starting focus pull-in of the target layer to the optical head 20. Here, the optical head control unit 10 outputs a focus pull-in instruction for performing the focus pull-in to L0 to the optical head 20. When the optical head 20 acquires the focus pull-in instruction output from the optical head controller 10, the optical head 20 starts focus pull-in to L0.

  In S305, the data conversion unit 30 acquires the electrical signal output from the detector 27 after the focus pull-in is started, and converts it into an FES and SUM signal. Then, the target layer detection unit 31 determines whether or not the focus pull-in is successful from the FES or SUM signal converted by the data conversion unit 30.

  When the target layer detection unit 31 determines that the focus pull-in is successful (YES in S105), the spherical aberration correction is terminated. When the target layer detection unit 31 determines that the focus pull-in has failed (NO in S105), the data conversion unit 30 outputs the FES and SUM signals to the spherical aberration correction value calculation unit 40.

  Next, in S306, the spherical aberration correction value calculation unit 40 changes the spherical aberration correction value BE again by changing the value of α. Then, the spherical aberration correction value calculation unit 40 outputs the changed spherical aberration correction value BE to the optical head control unit 10. Then, the spherical aberration correction unit 12 adjusts the position of the collimator lens 22 in the optical axis direction by the spherical aberration correction value BE acquired from the spherical aberration correction value calculation unit 40, and performs spherical aberration correction. Then, the process returns to S304.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and can be obtained by appropriately combining technical means disclosed in different embodiments. Embodiments are also included in the technical scope of the present invention.

  The present invention can detect the reflected light from the desired recording layer according to the intensity of the reflected light from the optical disk having a multi-layered recording layer and draw the focus, so that the optical disk with the multi-layered recording layer is reproduced. It can be used for an optical disk device for recording.

DESCRIPTION OF SYMBOLS 1 Optical disk apparatus 10 Optical head control part 11 Focus servo control part 12 Spherical aberration correction part (spherical aberration correction means)
13 Reproduction power control unit 20 Optical head 22 Collimator lens (spherical aberration correction means)
23 Objective Lens 25 Laser Light 27 Detector 30 Data Conversion Unit 31 Target Layer Detection Unit 40 Spherical Aberration Correction Value Calculation Unit 60 First Recording Layer (Recording Layer, Reference Recording Layer)
61 Intermediate layer 62 Second recording layer (recording layer)
63 Cover layer (protective layer)
65 Optical disc (optical recording medium)
66 Optical disc (optical recording medium)

Claims (3)

Laser light is incident on an optical recording medium in which a protective layer and a plurality of recording layers are arranged, and based on the intensity of the reflected light of the laser light from the plurality of recording layers, the plurality of recording layers Among them, an optical disk device for detecting a recording layer for recording or reproducing information,
Spherical aberration correcting means for correcting the spherical aberration generated in the laser light based on the intensity of the reflected light,
The spherical aberration correction unit is configured to determine a spherical aberration with respect to a reference recording layer, which is a recording layer arranged farthest from the protective layer among the plurality of recording layers, with respect to a position where the reference recording layer is provided. Correct with a spherical aberration correction value that matches the position opposite to the position where the protective layer was placed ,
And a spherical aberration correction value calculating means for calculating the spherical aberration correction value from the intensity of reflected light from the optical recording medium,
The optical disc apparatus characterized in that the spherical aberration correction means corrects the spherical aberration based on the spherical aberration correction value calculated by the spherical aberration correction value calculation means .   2. The optical disk apparatus according to claim 1, further comprising laser light intensity control means for controlling the intensity of the laser light.   Laser light is incident on an optical recording medium in which a protective layer and a plurality of recording layers are arranged, and based on the intensity of the reflected light of the laser light from the plurality of recording layers, the plurality of recording layers Among them, an optical disc recording / reproducing method for detecting a recording layer for recording or reproducing information,
  A spherical aberration correction step of correcting the spherical aberration generated in the laser light based on the intensity of the reflected light,
  In the spherical aberration correction step, the spherical aberration with respect to the reference recording layer, which is the recording layer arranged farthest from the protective layer among the plurality of recording layers, is determined with respect to the position where the reference recording layer is provided. Correct with a spherical aberration correction value that matches the position opposite to the position where the protective layer was placed,
  And a spherical aberration correction value calculating step of calculating the spherical aberration correction value from the intensity of reflected light from the optical recording medium,
  In the spherical aberration correction step, the spherical aberration is corrected based on the spherical aberration correction value calculated in the spherical aberration correction value calculation step.

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